1. Field of the Invention
The present invention relates to a three-dimensional ultrasonic scan probe including a plurality of ultrasonic transducer elements that transmit ultrasonic beams and receive echoes so as to enable real-time three-dimensional monitoring of a region to be measured.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 57-185840 has disclosed an ultrasonic diagnostic equipment in which ultrasonic transducer elements are arranged two-dimensionally in the form of a matrix in order to observe an organ or the like entirely. Any of the ultrasonic transducer elements is selected one after another and driven to transmit an ultrasonic beam with which an organ is electronically scanned. Echoes returned from the organ are synchronized and synthesized with one another. Consequently, a tomographic layer of the organ can be monitored.
However, when the equipment is used to monitor the entire heart, although a three-dimensional image can be produced based on echoes of ultrasonic beams that are transmitted from the numerous ultrasonic transducer elements and that pass an intercostal part, signal processing is complex. Moreover, since the ultrasonic transducer elements must be arranged mutually closely, the equipment becomes large in size. The equipment may be suitable for gynecologic examination rather than cardiology examination.
On the other hand, Japanese Unexamined Patent Publication No. 58-163348 (U.S. Pat. Nos. 4,570,488 and 4,580,451) has disclosed an ultrasonic sector scan probe including an acousticlens. For enabling observation of the entire heart through an intercostal parts, a plurality of ultrasonic transducer elements are arranged so that ultrasonic beams transmitted from the ultrasonic transducer elements will intersect at a point to scan the heart in the form of a sector. An acoustic line is a locus of an ultrasonic beam. At this time, the acoustic lines are focused near the point of intersection at a measurable depth. The plurality of transducer elements are grouped in order to focusultrasonic beams in the form of a beam, and selected successively. Consequently, the heart is electronically scanned in the form of a sector. However, since an equipment including the probe is designed in order to monitor a two-dimensional tomographic layer, the equipment cannot produce a three-dimensional image of the heart by electronically scanning the heart with ultrasonic beams transmitted through an intercostal part.
Accordingly, an object of the present invention is to provide a three-dimensional ultrasonic scan probe for electronically scanning a region to be measured through a narrow part so as to enable three-dimensional observation of the object.
According to the present invention, there is provided a three-dimensional ultrasonic scan probe including a plurality of ultrasonic transducer elements that transmit ultrasonic beams and receive echoes so as to enable three-dimensional observation of a region to be measured. The plurality of ultrasonic transducer elements are arranged on the top surface of the probe, which is a concave spherical surface, so that ultrasonic beams transmitted from the ultrasonic transducer elements will intersect at a point coinciden twith the center of curvature of the top surface, and then conically propagate over the region to be measured located beyond the point of intersection.
Ultrasonic beams transmitted from the ultrasonic transducer elements intersect at a point coincident with the center of curvature of the top surface of the probe. After passing through the point of intersection, the acoustic lines three-dimensionally and conically propagate over the region to be measured located beyond the point of intersection. Namely, the ultrasonic beams are transmitted to a wide region located beyond the point of intersection that occupies an intercostal part or any other limited part of a human body, and echoes returned from the wide region are then received. In other words, the plurality of acoustic lines are irradiated three-dimensionally after passing through the common point of intersection. Consequently, the wide region is monitored three-dimensionally through the narrow space or any other narrow limited part.
Moreover, an acoustic lens may be placed on the top surface of the probe. A plurality of ultrasonic transducer elements may be arranged on the incidence surface of the acousticlens so that ultrasonic beams transmitted from the ultrasonic transducer elements will intersect at a point coincident with the focus of the acoustic lens, and conically propagate over a region beyond the point of intersection. In this case, the acoustic lines are three-dimensionally and conically irradiated to the region beyond the point of intersection coincident with the focus of the acoustic lens. Consequently, the entire heart or the left ventricle of the heart is monitored through an intercostal part.
In particular, for three-dimensionally monitoring the heart through an intercostal part, the three-dimensional ultrasonic scan probe is placed on the chest so that a point at which ultrasonic beams intersect will be located in the intercostal part. In this state, a maximum angle of diffusion at which the transmitted ultrasonic beams diffuse after passing through the point of intersection is preferably set to an angle permitting the ultrasonic beams to cover the entire heart or a portion of the heart that should be diagnosed. Consequently, despite the simple structure, the probe makes it possible to diagnose in real time a change in the volume of the entire heart or a portion of the heart through an intercostal part.
For enabling electronic scan using a larger number of acoustic lines than the limited number of ultrasonic transducer elements arranged near a narrow space, an electronic scanning means is used in combination with the plurality of ultrasonic transducer elements. The electronic scanning means successively selects a plurality of combinations of adjoining ultrasonic transducer elements, and drives each combination of ultrasonic transducer elements to transmit ultrasonic beams simultaneously. Owing to the electronic scanning means, a larger number of acoustic lines than the number of ultrasonic transducer elements can be transmitted to scan a region. This leads to improved accuracy in measurement, intensified ultrasonic power that is higher than the ultrasonic power offered by each ultrasonic transducer element,and an extended detection range.
The maximum angle of diffusion at which the ultrasonic beams transmitted from such plurality of ultrasonic transducer elements diffuse after passing through the point at which the ultrasonic beams intersect can be also set to an angle, which permits the ultrasonic beams to cover the entire heart, with said three-dimensional ultrasonic scan probe placed on the chest so that the point of intersection will be located in an intercostal part. This maximum angle of diffusion at which the ultrasonic beams diffuse is preferably set to approximately 60xc2x0.